Recent years have seen the development of numerous optically readable discs. The first was the compact disc (CD) for digitally recorded music. Generally 12 centimeters in diameter and 1.2 millimeters in thickness, the disc contains a spiral track much like a standard long playing (LP) music record. Rather than analog information being stored in the side to side movements of the track as with the LP record, however, digital information on the CD disc is stored as minute optical variations in the surface of the track. These variations, in one optical recording technique, consist of surface pits created by a laser beam. It is the length of these pits and the distance between them that is later read by a focused laser beam in a CD player as digital "ones" and "zeros" which are then processed into the original musical signal from which they were derived.
More recently this technique has been extended to compact disc read only memories (CD-ROM) for personal computers. Although they cannot be written to, as with a computer floppy or hard disc, they can store a truly impressive amount of read only information. One example is the complete Webster's Ninth New Collegiate Dictionary, complete with pronunciation, illustrations and geographic place names on one disc. The capability of such storage has also been taken advantage of by using laser discs for storing video information which can then be decoded and displayed on a television set.
While such optically readable discs are relatively rugged and forgiving of minor scratches, dust and debris, they still must be stored and given sufficient protection--scratches that sufficiently scatter the laser beam can block reading of the encoded information. A disc protective container also serves for the display of a label that attracts the buyer and informs the user of the disc. The industry standard CD protective container 20 is illustrated in FIG. 1. It consists of a platform 22 on which the disc 42 is held and a cover 24. The cover 24 is pivotally mounted by means of a hinge 26. The platform 22 has a shallow end wall 28 while the cover 24 has a pair of side walls 30 and 32. Small projections 34 and 36 on the inner surface of each side wall 30 and 32 press into platform holes 38 and 40 to hold the cover 24 in place.
The disc center hole 46 is pressed onto a platform resilient boss 48 while the disc 42 fits into platform depression 50. The platform has reliefs 52 and 54 to aid the user in grasping the disc edge 44 in order to remove the disc 42 from the boss 48 and platform 22, once the cover 24 has been rotated out of the way.
There are several problems presented by this container. Because the cover 24 and platform 22 are molded of clear polystyrene (the platform 22 is actually formed of two parts-one including the boss 48 is usually of polypropylene) it is difficult to distinguish them. Consequently, it is not uncommon for the user, in attempting to grasp the platform 22 with one hand, to mistakenly place the thumb and fingers of that hand on the cover side walls 30 and 32 (thinking them to be parts of the platform) while correctly placing the fingers of the other hand on the platform back wall 56 and lifting, with the thumb of that hand, the cover front border 58. Since both hands are inadvertently holding the cover 24, the container 20 can not be opened.
The proper technique for opening the container 20 is to place the fingers of both hands on the platform back wall 56, the thumb of one hand on the platform end wall 28 and, with the other thumb, lift the cover front border 58. While this works reasonably well, once one is experienced, two problems resulting from the container design, can still cause annoying problems.
The first comes when the hand that lifted the cover 24 is removed to grasp the disc 42. When this is done the cover rotates back, as shown at 24' to where the cover rear border 60 rests on the fingers of the hand still holding the platform back wall 56. This is uncomfortable. If the user moves the figures so as to allow the cover 24' to lie flat in the same plane as the platform 22, there is nothing left for the fingers to hold on to and control of the container 20 is less than complete.
The other problem results from the relative proportions of the platform 22 and cover 24. If the size of a cover relative to the container it is associated with is small, as it is with the familiar audio tape cassette case, one feels comfortable as the cover lifts up because the relative size and mass remains with the container. However, in the design of the industry standard CD container 20, when the cover 24, which is equal in size and mass to the platform 22, pivots upwards the user is often surprised by a sense that the whole container is suddenly moving. The effect can be so unexpected, combined with a resultant change in the center of gravity, as to cause the container to be dropped.
Ironically, in view of the opening difficulties posed by the container 20, it can sometimes open too easily. This problem occurs, when the user attempts to simply lift the container 20 with the fingers and thumb of one hand on opposite cover side walls 30 and 32. The length of the cover 24' affords the mass of the disc 42 and platform 22 considerable leverage and the resultant force overcomes the starting friction of the projections 34, 36 and holes 38, 40. The user suddenly has an open container dangling in space or, worse, a disc falls to the floor.
Still another problem comes when the container 20 is open. It then occupies considerable space since the cover 24' lies in the same plane as the platform 22 and doubles the size of the closed container. If two or three discs are in use at one time, the amount of working area obscured can become quite large.
U.S. Pat. Nos. 3,899,229, 4,046,255, 4,428,480 and 4,493,417 to Ackeret address some of the opening difficulty problems described above by the use of sliding disc holders but still share the problems that result from the case size increasing when in the open state.
U.S. Pat. Nos. 4,422,034 and 4,655,344 to Ackeret and U.S. Pat. No. 4,875,578 to Nehl are containers for multiple discs in which hinged slides are employed to reduce the size of the open container but these solutions are only partially successful.
U.S. Pat. No. 4,463,849 to Prusak shares the problem of increased size in the open state with the industry standard container but adds strips of material as brushes to clean dust and debris from the container walls. However, the brushes do not remove the contaminants from the disc itself.
Because of the problems reviewed above and the growing use of optically readable discs, it can be seen that a container that would open easily and safely, be obvious in the method of its use, and not use any more space, when open, than a disc itself, would be of considerable utility.